A foster mum is facing a charge of murder over the death of a 20-month-old-boy in NSW.Image: 7NEWS

A woman accused of murdering a 20-month-old foster boy was seen physically forcing the child into a bath on the night of his death, police will allege.

The woman’s daughter was so scared of her mother’s temper, court documents state, that she locked herself in her bedroom with another sibling while listening to the child’s screams.

The 41-year-old woman, who faced Dubbo Local Court for a committal hearing on Wednesday, has not entered a plea to one count of murder.

The toddler was found unresponsive in his bed by paramedics on March 23, 2015, after the foster mother called triple 0.

He could not be revived.

Police will further allege the foster mother instructed her daughter not to tell investigators about the bath incident when she was interviewed by police in the days after the child’s death, court documents reveal.

Blunt force trauma

The woman, who cannot be named for legal reasons, sat stony-faced throughout the hearing.

She fidgeted at times when the graphic details of the child’s injuries were detailed.

The court heard blunt force trauma to the little boy's head was the most likely cause of death but that he also suffered a broken femur.

The break was so severe, a pathologist compared the injury to that sustained in a high-speed car crash, the court was told.

The child also was found with vomit in his mouth, and had a penetrative injury to his bottom, described by a trauma specialist as “forceful”.

Varying accounts

The foster mother, who has three biological children of her own, has given multiple, varying accounts of what happened on the night of the child’s death.

Court documents claim that in a police recording between the accused and her partner, the foster mother said she “lack(ed) clear memory about the event”.

“Wouldn’t hitting your head against a bath that many times give you a head injury,” the foster mother told her partner in the recording.

The accused claims the child hated baths and would “crocodile roll” when she tried to bathe him.

'Not consistent'

“(The) pattern of head injuries is not consistent with the alleged story of this infant crocodile rolling was in a bath,” he wrote in his report.

“I am of the opinion there had been a number of applications of blunt force trauma to the head.

Chevron Right Icon'I am of the opinion there had been a number of applications of blunt force trauma to the head.'

“This may have occurred either by striking an object against the head or by banging their head against an object.”

The accused, her three biological children and her partner, were at their home, 100km from Dubbo, on the night of the child’s death.

Revelations of the child’s murder rocked the state’s embattled child protection system and followed a 7NEWS investigation.

At the time of the woman’s arrest, the child’s biological mother said she had been “left in the dark” and was desperate for answers, after giving the child over to Family and Community Services until she could remove herself from a domestic violent environment.

The child was given to foster care provider Uniting to find a suitable carer.

Three months later, he was dead.

The child’s biological mother died in January this year, without seeing justice for her son.

Long-term placement

Court documents show that when the foster mother took care of the child, she was hoping to have him in a long-term placement.

But she was angered when she was notified of the “temporary” nature of the placement in the weeks before his death.

The family at the centre of the murder allegation had provided foster care in the past and had attended a "gathering" at the accused's brother-in-law's, on the night of his death.

The accused told police she had consumed five to six beers that night.

Shocking cases

Revelations of the little boy’s death followed the shocking case of Girl X, a 15-year-old girl who died of a drug overdose in a residential foster care home in Sydney’s inner-west just one year after she was allegedly raped by a youth worker in another.

Less than a year later, a five-year-old boy passed away under the watch of foster carers with a burn on his back and a cocktail of drugs in his system.

An autopsy report revealed the five-year-old had cockroach bites on his neck. His case is still before the Coroner.

All three children died while under the care of Uniting.

Uniting is still accredited to provide foster care in New South Wales.